Starting device for electric motors.



G. D. KNIGHT. STARTING DEVICE FOR ELECTRIC MOTORS. APPLIOATION FILEDmums, 1907.

91 3,5 1 2, Patented Feb. 23, 1909.

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STARTING DEVICE FOR ELECTRIC MOTORS.

APPLICATION FILED JAN. 26, 1907.

Patented Feb. 23, 1909.

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U N ITED- STATES PATENT OFFI( 3131. CHARLES D. KNIGHT, OF SGHENECTADY,NEWTOT, ASSIGXOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

STARTING DEVICE FOR ELECTRIC MOTORS.

Specification of Letters Patent.

Patented Feb. 23, 1909.

Application filed January 26, 1907. Serial No. 354,229.

To all whom it may concern:

Be it known that I, CHARLES D. KNIGHT, a citizen of the United States,residing at Schenectady, county of Schenectady, State of New York. haveinvented certain new and useful Improvements in Starting Deices forElectric Motors, of which the following is a specification.

This invention relates to means for controlling electric motor circuitsand has for its object the provision of a device of this character inwhich the main armature circuit is automatically opened by meansexternal to the controlling device itself, provision being made wherebythe controlling element cannot be operated until the circuit is closedthrough the external means.

My invention relates more specifically to controlling devices of thetype used in start" ing electric motors. In this type of apparatus, thecontrolling arm is ordinarily spring-pressed to the off or st'artingposition and is held in the on or running po sition by a no-voltagerelease magnet. Upon failure of voltage, the arm returns to the offposition and the main circuit is broken on the rheostatic contacts. Thebreaking of the circuit on the contact studs is objectionable in manyinstances, especially when the current is heavy since the contacts arethereby burned andnmst be replaced.

In carrying out my invention I provide in connection with the ordinarystarting rheostat having a spring-pressed controlling arm and ano-voltage release magnet, a circuit breaker arranged to open the maincircuit before the arm reaches the off' position. I also provide meansfor preventing the closing of the motor circuit when unprotected by thestarting resistance. To do this, means are provided whereby thecontrolling arm cannot be moved from the starting position until theexternal circuit opening means has been operated to close the circuit.

In the accompanying drawings I have shown a starting panel equippe withmy invention.

In the drawings, Figure 1 is a front elevation of the device; F 2 is aside elevation of a portion thereof, certain parts being in section; andFig. 3 is a diagram of the circuits.

Referring to the drawings, 10 represents an insulating base of slate orsoapstone having mounted thereon a motor-starting mechanism of the usualtype and an automatic circuit breaker adjacent thereto which may also beof standard construction except as to details. The starting mechanismcomprises a plurality of starting contact segments 11 arranged in an arcof a- ClI'Cl and forming the terminals of a starting resistance 12. Acontrolling arm 13 pivoted at 14 is arranged to engage the contactsegments to vary the resistance and is biased to the starting positionby means of a spring 15. A no-voltage release magnet 16 is arranged toretain the controlling arm in the running position as shown in Fig. 1,and the controlling arm is provided with a bridging contact 17 forclosing the armature circuit so as to short circuit the controlling armwhen the latter is held by the. retaining magnet. The automatic circuitbreaker is preferably of standard construction.

The particular circuit breaker which I have shown is of the general typedescribed and claimed in the patent to E. M. Hewlett, No. 840,848,although, of course, any other suitable circuit breaker will serve thepurpose. The rheostat and the circuit breaker each other that they canbe conveniently interlocked so that means can be provided whereby thearm of the rheostat will trip the circuit breaker. In order to bringabout the tripping operation I provide a bell crank lever having a longarm 18 and a short arm 19 pivoted at 20. The long arm of the lever isnormally in the path of the rheostat arm 'and the short arm engages afinger 21 mounted on the pivot 22, to which the circuitbreaker latch 23is secured. The lever being normally in the position shown in full linesin Fig. 1 when the rheostat arm 13 is moved to the starting position, itengages the long arm of the lever and forces it to the position shown indotted lines. This causes the short arm 19 to engagethe finger 21 whichmoves the latch 23 against a spring tension out of engagement with thecircuit breaker. The circuit breaker thereupon opens, breaking the motorcircuit at the main laminated contact 24 and shunt contacts 25 and 26.So long as the rheostat lever is left in this start- I ing position, thecircuit breaker cannot be are so located on the base with reference totor circuit without any protective resistance in the circuit, I providean interlocking mechanism so that itis impossible to move thecontrolling arm until the circuit breaker is closed. I have accomplishedthis result in the present instance by providing a pin 27 mounted in abar 28 beneath therheostat base, so as toproject up through the slatebase and prevent movement of the controlling arm. The bar 28 is pivotedat 29 and its free end is spring-pressed inward by means of a spring 30.This bar also carries a pin 31 nearitsfree end, which is engaged "by themovable element of the circuit breaker. As shown in the drawings thispin is engaged by the yoke 32 which secures the main contact 24:, andthe arrangement is such that when the circuit breaker is closed the yoke32 forces the pin 31 and bar 28 outward. This movement of the bar movesthe stop pin 27 outward so that it no longer opcrates as a stop to thearm 13. The circuit breaker then being closed, the controlling arm maybe moved to rimning position Where it is held by the retaining magnet.In Fig. 1 the parts are so arranged that the controlling arm 13 may bemoved over the first three contact segments before reaching the stop pin27. The movement of the contactor' over these segments, however, doesnot affect the circuit since they are all connected; together and as awhole constitute the first starting step, there being no dead oropen-circuiting segment. The arrangement of the circuits is clearlyillustrated in Fig. 3. Current passes from the line L through the motorarmature A across the circuit breaker cont-acts 24 through the overloadtrip coil of the circuit breaker 33 thence to the controlling arm 13,starting resistance 12 and back-to line at L. When the rheostat is inrunning position, the bridging contact 17 short circuits the resistanceacross the-contacts 34. The retaining magnet 16 is preferably connectedacross the line as shown.

To start the motor, the circuit breaker must first be closed so as toremove the stop pin 27 fromthe path of the controlling arm. This beingdone, the arm may be moved to running position in the usual way. Uponfailure of voltage the controlling arm will return to the startingposition and as 1t does so it will engage the arm IS'and trip thecircuit breaker, thereby opening the main circuit on the circuit breakercontacts instead of onthe contact segmentsof the rheostat. Upon overloadthe circult will, of course, be opened upon the circult breaker contactsin the usual way. The pin 27 is provided with a beveled head so that incase the circuit breaker opens first so as to project the pin up throughthe base, the controlling arm will pass over the pin by engaging thebeveled portion and forcing it downward. It will thus be seen that Ihave provided a very convenient and eflicient interlocking mechanismbetween the rheostat and circuit breaker, which protects the segments ofthe rheostat and at the same time protects the motor against the rush ofcurrent occasioned by the closing of the circuit without the protectingreslstance. Itshould be understood, of course, that the particularconstruction which I have shown and described is for purposes ofillustration merely, since many modifications thereof will suggestthemselves to those skilled in the art which do not depart from thespirit of my invention, the scope of which is set forth in the annexedclaims.

What I claim as new. and desireto secure by Letters Patent of theUnitedStates, is,

1. The combination with a starting rheostat having a spring-returned armand a no-voltage magnet for retaining the same in running position, ofan automatic circuit breaker in circuit with said arm, means forpreventing the movement of said arm from the starting position Whilesaid circuit breaker is open and means for automatically opening saidcircuit-breaker when the arm 1s moved towards starting position.

2. The combination with a'starting rheostat having a spring-returned armand a no-voltage magnet for retaining the same in running position, ofan automatic circuit breaker in circuit with said arm, means wherebysaid circuit breaker is tripped as the arm returns to starting position,and means for preventing the movement of the arm toward running positionwhile the circuit breaker is open.

3. The combination with a starting rheostat having a spring-returned armand a no-voltage magnet for retaining the same in running position, ofan automatic magnetic circuit breaker in circuit with the arm, meanswhereby said breaker is tripped as the arm returns to starting position,and means for preventing the movement of the arm toward running positionwhile the circuit breaker is open. v

4. The combination with a circuit controller provided. with automaticno-voltage no-voitage magnet for retaining-the same in said stop andallows the arm to be moved running posit1on,- of an automatic circuit torunning position. 10 breaker, means whereby said breaker is In witnesswhereof, I have hereunto set tripped as the cont-rollingelement movestomy hand this 25th day of January, 1907.

ward starting position, a stop normally in the CHARLES D. KNIGHT.

path of the controlling arm when the latter \Vitnesses:

is in the starting position, and means where- BENJAMIN B. HULL,

by the closing of the circuit breaker removes HELEN ORFORD.

